We have found that infection of TC7 cells, African green monkey kidney cells, with Simian virus 40 stimulates host antigens which locate in the centriolar region of cells. The centriolar antigens consist of two polypeptides with molecular weight of about 14K and 17K daltons. The stimulation of the antigens is a result of de novo protein synthesis which occurs very early in infection, 0 to 5 hours after infection. The centriolar antigens are induced in cells infected with temperature-sensitive mutants of all complementation groups (tsA, tsB, tsC, tsBC and tsD) at restrictive temperature but not in cells infected with viable deletion mutants which contain deletions in the region of little-t gene (0.54-0.59 map units) and exhibit reduced transforming ability. Antigenically related protein(s) exists in ciliated epithelial cells isolated from chicken trachea and the related antigen(s) is localized at basal bodies of the cells. Our specific aims are: (1) to study the nature of the antigens; (2) to study the nature of the antigen stimulation; (3) to study the involvement of the antigens in various transformed cells and in cells at the particular phase of cell cycle; (4) to study the presence of the related antigens in other cells; and (5) to study the localization of antigens at the supramolecular level.